Method and means for feeding powdered fuel



W. M. BAXTER.

METHOD AND MEANS FOR FEEDING POWDERED FUEL.

APPLICATION FILED'APR. 21. 19I8. RENEWED 05c. 24.19l9.

Patented Oct. 12, 1920.

2 SHEETS-SHEET 1.

' QWJnz/enir W. M. BAXTER.

METHOD AND MEANS FOR FEEDING POWDERED FUEL. APPLICATION man APR. 21, 1918. RENEWED DEC. 24.1w),

1,355,444. Patented Oct. 12, 1920.

2 SHEETS-SHEET 2.

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WILLIAM H. BAXTEB. OF CHICAGO, ILLINOIS, ASSIGNOR '10 MILTON W. ABBOWOOD, OF CHICAGO, ILLINOIS.

METHOD AND MEANS FOR FEEDING POWDERED FUEL.

Specification of Letters Patent.

Patented Oct. 12, 1920.

Application filed April 27, 1918, Serial No. 231,070. Renewed December 24, 1919. Serial No. 347,200.

To all whom it may concern:

Be it known that 1, WILLIAM M. BAXTER,

a citizen of the United States, residing at which the following is a specification.

This invention relates in general to method and means for feeding powdered fuel, and has moreparticular reference to the feeding of powdered coal and the thoroughly mixing therewith of the requisite amount of air so as to promote the highest combustive efliciency.

I am aware that prior to my invention 7 various methods and apparatus have been employed with a view of mixing ,air and powdered coal, but in many of these systems now in use a considerable prop rtion of the air employed for maintaining, combustion is delivered directly to the combustion chamber instead of being supplied by the feeding apparatus. In other words, the fuel when delivered to the combustion chamber is only partially mixed with air, and the particles of fuel, therefore, are not sufiiciently separated one from another with the result that the imperfect mixture fed to the combustion chamber does not burn evenly or instantaneously. Constant attention to such furnaces is required in order to maintain even an approximately efiiient operation, and the slag compounds resulting from comparatively low and uneven temperatures in the combustion chamber are deposited throughout the chamber, and in the case of a boiler, for instance, are even carried over into the tubes with very serious results for the reason that the low oxids resulting from low combustion temperatures are when hot exceeding stifi', plastic and tenacious, and when cold, extremely hard and difficult to remove. The high oxids, on the other hand, resulting from high combustion temperatures, such as I secure by perfect mixing and instantaneous combustion, are very fluid and flow freely when invention is the provision of a method and apparatus by which the powdered fuel is thoroughly diffused and commingled with the requisite amount of air to properly and completely support combustion. In other words,' my invention is designed to thoroughly separate the various particles of fuel, and deliver each particle to the-combustion chamber substantially equi-distant from every other particle, and immediately surrounded by the proper amount of air for its combustion.

Another object of the invention is to deliver all of the air to the combustion chamber along with the fuel so that it will not only thoroughly separate and diffuse the fuel particles throughout the air, but by this method the air may be accurately controlled, and the proportions of air andfuel so regulated that highest efliciency in the combustion chamber will result, and when once the apparatus has been set it will re= quire no further attention so long as ti 1; character or quality of the fuel is uniform? In some types of furnaces it is desirable to deliver to the combustion chamber a regulated quantity of highly heated air, in addition to the relatively cool or partially heated air delivered with the fuel. Another object of my invention is to so deliver the mixture of fuel and air to the combustion chamber that upon coming in contact with the highly heated air, the mixture of fuel and air will be immediately expanded, thus further separating and diffusing, by ex pansion, the fuel particles vthrough the heated air so as to promote instantaneous and perfect combustion without the necessity of employing a commingling jet or jets in conjunction with deflecting bridge walls and the like which has heretofore been considered necessary.

Instead of relying upon the subjection of the outside of a stream of fuel to the action of air currents as has heretofore been done for the purpose of commingling the air and fuel, I propose to deliver the air radially outwardly into a stream of fuel, and to produce cross'currents and eddies of air in the fuel stream which will insure a thorough commingling of the air and fuel, and rethoroughly separated particles, each surrounded by suflicient air to insure its combustion in the combustion chamber.

For the purpose of facilitating an understanding of my invention, I have illustrated in the accompanying drawings one practical and preferred apparatusby which my improved method may be carried out...

Referring to the drawings Figure 1 is a vertical sectional view through an apparatus adapted to carry out my improved method;

Fig. 2 is an end view looking at the lefthand end of the apparatus shown in Fig. '1;

Fig. 3 is an end view of the delivery nozzle and mixing chamber; and- Fig. 4 is a sectional view on the line 44 of Fig. 1.

In the drawings reference character 5 indicates a coal chute or hopper in which the powdered fuel is stored, and from which it feeds downwardly to a screw conveyer 6 rotatably mounted in suitable bearings and adapted to operate in a cylindrical housing 7. This conveyor, as will be noted, comprises a shaft 8 provided with a worm and is driven from a motor 9 through a shaft 11 which is equipped with a worm adapted to mesh with and drive a worm wheel mounted upon the shaft 8, the worm and worm wheel being disposed within the housing 12.

As the powdered fuel is fed to the left, viewing Fig. 1, by the screw conveyer it is first subjected to a stream of air which is admitted into the housing 7 through a pipe 13. A fan blower (not shown) of any preferred construction is attached to the pipe 13 and serves to deliver the stream of air to the fuel under the requisite pressure. The air and fuel together continue to travel to the left, viewing Fig. 1, into a horizontally disposed cylindrical member 14 having its open end arranged in the path of travel of the air and fuel. This member is provided with circumferential apertures 15 through which the air and fuel are delivered radially outwardly in a direction at right angles to the original direction of travel of the fuel and air. This change in direction of the fuel and air, together with its division into small streams passing outwardly through the apertures in the member serve to comminglethe air and fuel to a considerable extent, and this commingling is further augmented by rotation of the member 14. The member is mounted, as will be observed from Fig. 1, upon the shaft 8 and rotates therewith so that any chunks or lumps of fuel are shaken about and broken up until sufliciently pulverized to pass through the apertures 15 in the walls of the member. The apparatus thus far described is known as the coal control, and by varying the speed of the screw conveyer the amount of fuel fed to the furnace may be regulated. In some instances the screen member 14 may be stationarily mounted instead of rotatably mounted upon the shaft. The air admitted through the pipe 13 is usually about one-half the amount required in the combustion chamber, and the purpose of this part of the apparatus is to regulate the amount of coal and to diffuse the coal as thoroughly as possible throughout the air admitted at this stage.

After passing through the screen member 14 the stream of air and fuel flows downwardly through the passageway 16 into a burner or mixer indicated generally by reference character 17. This mixer is cylindrical in form and consists of a plurality in the present instance four concentrically arranged cylinders numbered 18, 19, 21 and 22, respectively. These four cylinders provide four conduits or passages 23,24, 25 and 26, respectively but obviously the number of cylinders and resultant passages may be increased or diminished according to the requirements of any particular installations. The conduits 23 and 25 are the fuel pass-ages through which the fuel and air from the screen member 15 pass from one end of the mixer to the other, and communication is established at the left end of the mixer between the passages 23 and 25 through a se ries of small pipes 27 shown in Figs. 1 and 4. The passages 26 and 24 are air passages and communication is established between these two passages around the pipes 27, as will be evident from Fig. 1. Air under pressure is supplied to the conduits 24 and 26 from a fan blower or air compressor of any preferred type, preferably the same one to which the pipe 13 is connected, connected by means of suitable piping to the coupling 28 at the left-hand end of the mixer. The right-hand ends of the conduits 25 and 23 are open except for supporting webs or brackets 29 which support the right-hand .ends of the cylinder, while the right-hand end of the chamber 24 is closed by a ring or flan e 31. c

The fuel and air from the screen member 15 are delivered through the passageway 16 to the left-hand end of the mixer where the stream is divided and flows in two hollow cylindrical streams through the conduits 23 and 25, respectively. Air under pressure admitted atthe left-hand end of the mixer through the coupling member 28 flows into the conduits 26 and 24. The

conduit 26 is provided with a series of circumferentially arranged perforations 32 disposed in staggered relation with respect to each other, and the air flowing under pressure in the conduit 26 is discharged outthrough the conduit 25, and as these jets impinge against the outer walls of the conduit 25, that is, against the .inner faces of the cylinder 21, the jets are deflected and diffused, thereby setting up cross currents and eddies which serve to further and thoroughly separate the fuel particles and to uniformly commingle them. with the air.

The outer walls of the chamber 24 are likewise provided with jet apertures 33, through which jets of air are projected radially outwardly into the conduit 23, and

thoroughly commingle the fuel particles with the air so that a uniform mixture of the fuel with air is secured. Furthermore, since the aggregate cross sectional area of the fuel passages 23 and 25 is greater than that of the passage 16, the fuel in these annular passages is under a reduced pressure. As a result of this reduction in pressure the fuel streams in these passages are rarified or expanded and when the air jets which are under higher pressure as the result of the proportions of the passages through which the air is conducted, are projected into these rarefied fuel streams the jets rapidly expand or open up within the fuel passages, thereby establishing the most favorable condition for the commingling of the'air with the fuel, which commingling is then completely accomplished not only by. the direct action of the jets, but also by the eddies and crosscurrents set up in these passages from the rebound of the jets and the cross firing of the currents.

Furthermore, the hollow traveling stream of fuel and air is more rare toward its periphery than toward the center and the radially issuing jets of air therefore encounter progressively less resistance as they penetrate through the stream. This fact results in an increased expansion of the jets beyond the normal expansion which takes place in accordance with the laws governing the expansion of fluid streams issuing from restricted orifices, which causes a progressive commingling of the air and fuel in the apparatus-and thus facilitates the complete mingling.

The two hollow streams of fuel and air issuing from the right-hand ends of the conduits 23 and 25 enter a tapering head or end member 34 which is gradually re duced incross-sectional area and is connected at its extremity with the discharge noz-,

zle 35 which discharges directly into the combustion chamber 36. This discharge nozzle, as will be evident from Fig. 3, is flat and quite wide in proportion to its hei ht so that the issuing stream of thoroughly commingled fuel and air is discharged into the combustion chamber in a substantially flat stream which presents a maximum surface are and readily diffuses throughout the combustion chamber and burns with high efficiency. 7

The right-hand end of the inner air cylinder 22 is also tapered and terminates in a discharge orifice or nozzle 37 which directs a jet of air into the outflowing stream of air and fuel in a direction longitudinally of the stream and toward the discharge nozzle, thus further diffusing and mixing the fuel with the air. This mixing is facilitated also by the shape of the tapered-head member 34 which is designed to set up cross currents and eddies which are conducive to a thorough-mixing of the air with the fuel.

It will be manifest from the foregoing that by causing the air and fuel to travel in certain defined directions, and by projecting radially outwardly into the streams of air and fuel jets of air under pressure which set up cross currents and eddies, I am enabled to supply to the combustion chamber all of the air necessary to support combustion of the fuel at the requisite temperatures, and am enabled to deliver the fuel in finely divided condition, each particle separated from the other particles and surrounded by the requisite. amount of air for its combustion. Since the quantity of air and the quantity of fuel can be varied and regulated to a fine degree of nicety, a proper mixture can be readily secured and accurately maintained, and this mixture is such that'instantaneous combustion is produced in the combustion chamber, which causes the ash to be separated into highly-fluid slag and impalpable infusible powder. Furthermore the instantaneous combustion resulting fromthe perfect mixture immediately burns any sulfur which may remain in the fuel with the result that the process is applicable in metallurgical work for the use of low grade sulfur coals which have not been available heretofore with the older firing methods.

It is believed that my improved method and one practical apparatus for carrying the same into effect will be readily understood from the foregoing without further description, but it should be obvious that the method, and also the apparatus for carrying it into effect, are capable of considerable modification without departing from the essence of the invention as set forth in the following claims I claim:

1. The method of feeding powdered fuel which consists in subjecting a mass of fuel, to a stream of air under pressure, dividing the resultant stream of fuel and air into a plurality of streams directed radially outwardly from the direction of travel of the original resultant stream, collecting said plurality of streams into a cylindrically formed stream, and delivering radially out wardly into said cylindrical stream a plurality of jets of air under pressure.

2. The method of feeding powdered fuel which consists in subjecting a mass of fuel 7 to a stream of air under pressure, causing v the resultant stream of fueland air to assume a cylindrical shape, delivering radially outwardly into said cylindrical stream a plurality of jets of air under pressure, converting said cylindrical stream into a solid stream of less cross-sectional area, and delivering said stream under pressure to a point of combustion.

4. The method of feeding powdered fuel which consists in subjecting a mass of fuel to a stream of air under pressure, collecting the mixture of fuel and air into a hollow tubular stream, delivering radially out wardly into said tubular stream a plurality of jets of air under pressure, reducing said tubular stream into a solid stream and delivering the same under pressure to'a point of combustion.

5. In an apparatus of the character described, the combination of an air conduit provided with a series of circumferential apertures, a fuel conduit surrounding said air conduit and open at the ends thereof for the passage of fuel therethrough, a second air conduit surrounding said fuel conduit and communicating with said first-mentioned air conduit, saidsecond air conduit being provided with circumferential perforations, and a second fuel conduit surrounding said second air conduit and communicating with said first-mentioned fuel conduit. I

6. In an apparatus of the character described, the combination of a series of concentrically disposed aid and fuel conduits, the inner and alternate conduits being communicating air conduits, and the outer and alternate conduits being communicating fuel conduits, means for supplying fuel to said fuel conduits, means for supplying air under pressure to said air conduits, and means whereby air is projected radially outwardly in jets from said air conduits into said fuel conduits.

7. In an apparatus of the character described, the combination of an air conduit provided with a series of circumferential radially disposed apertures, a cylindrical fuel conduit surrounding said air-conduit with its surrounding walls in relatively -close disposed air and fuel conduits, means for delivering 'air and fuel under pressure to said conduits respectively, said air conduit being provided with radially disposed apertures through which air is delivered therefrom in radial jets into said fuel conduit 'andagainst the surrounding walls thereof,

and means for collecting into a solid stream the mixture of air and fuel from said fuel conduit and delivering said stream to a combustion chamber.

9. In an apparatus of the character described, the combination of a cylindrical fuel conduit, a cylindrical air conduit disposed concentrically within said fuel conduit said air conduit being provided with radially disposed apertures through which jets of air are projected radially outwardly into said fuel conduit, means for delivering air and fuel under pressure to said respective conduits, and means for delivering the resultant mixture from said fuel conduit to a pointof combustion.

10. In an apparatus of the character described, the combination of means for supplying a quantity of powdered fuel, means for delivering a stream of air thereto, a cylindrical member disposed in the path of travel of said air and fuel and provided with circumferential perforations through which the air and fuel are discharged from said member, and means for rotating said member.

11. In an apparatus of the character described, the combination of a cylindrical member open at one end and provided with circumferential perforations, means for delivering powdered fuel and air under pressure into the open end of said member, said fuel and air being discharged from the member through said perforations in a radial direction, a cylindrical conduit for receiving said fuel and air, an air conduit arranged in said cylindrical conduit and provided with circumferential perforations through which jets of air under pressure are delivered radially outwardly from said air conduit into the fuel conduit, and a delivery nozzle of reduced cross-sectional area connected with said fuel conduit through which the commingled air and fuel are delivered into a. combustion chamber.

12. In an apparatus of the character described, the combination-of'means for preliminarily mixin a quantity of powdered fuel with air un er ressure a cylindrical conduit throu h whic said an and fuel are delivered un r ressure, a stationar air conduit arrange within said cylin rical conduit and provided with circumferential perforations adapted to deliver jets of an under pressure radially outwardly into the fuel conduit, a discharge nozzle of reduced cross-sectional area connected with said fuel conduit, and means for delivering a jet of air into said fuel conduit in a longitudinal direction toward said nozzle.

13. The method of feeding powdered fuel which consists in preliminarily mixing a quantity of air with powdered fuel, converting-the resultant stream of fuel and air into a hollow cylindrical stream of increased cross sectional area, and causing a plurality of 'ets of air under pressure to penetrate sai hollow stream from the inside thereof and expand within said stream.

14. The method of feeding powdered fuel which consists in preliminarily mixing air with powdered fuel, converting the resultant stream of fuel and air into -a rarefied hollow cylindrical stream, and so projecting a pluralit of jets of air under pressure into said rare ed stream that the expansion of said jets will cause the fuel to be commingled with air.

15. The method of feeding owdered fuel which consists in preliminari y mixing air with powdered fuel, converting the resultant stream of fuel and air'into a hollow cylindrical stream, and causing jets of air un-' der pressure to pass transversely through said stream and be deflected back into said stream to further commingle said fuel with air.

16. The method of feeding powdered fuel which consists in preliminarily mixing air with powdered fuel, converting the resultant stream of fuel and air into a rarified cyv lindrical stream, projecting jets of air under pressure radially into said stream and causing said jets to expand and be deflected into sald stream.

17. The method of feeding owdered fuel I which consists in preliminarl y mixing air with powdered fuel, converting the resultant stream of fuel and air into a hollow cylindrical stream and projecting jets of air under pressure radially into said stream, so as to cause a progressive commingling between said jets and said stream.

WILLIAM M. BAXTER. 

